Các tính năng của hành tinh Trái đất mà làm cho nó trở nên đặc biệt là nước lỏng chất quan trọng đối với cuộc sống như chúng ta biết. Là một hợp chất đơn giản của hydro và oxy, nước có lẽ là phổ biến khắp vũ trụ, nhưng chủ yếu là dưới hình thức đá rắn hoặc hơi nước khí. | WATER AND ICE The feature of planet Earth that makes it so special is liquid water the substance that is vital to life as we know it. As a ATOMS AND MOLECULES Water is a mass of molecules each with two hydrogen atoms and one oxygen atom. This explains its chemical formula H2O. The molecules of liquid water are loosely bound by electronic forces enabling them to move in relation to each other. When water freezes the molecules become locked together and simple compound of hydrogen and oxygen water is probably common throughout the universe but mainly in the form of solid ice or gaseous water vapor. Both occur throughout the solar system but liquid water is rare mainly because the other planets are either too hot or too cold. Earth is unique in the solar system in having temperatures that allow all three forms of water to exist sometimes in the same place at the same time. when it evaporates they burst apart. Ice has a regular geometrical structure of water molecules Ice If water freezes the water molecules lock together in a crystal lattice to form the solid structure of ice. Water In liquid form the water molecules cling together but are able to move around each other and flow. Water vapor Heat energy breaks the bonds holding water molecules together so they move apart to create a gas. Ice forms a thin crust on the sand dunes of this crater floor on Mars 4 WATER IN SPACE Water is constantly careening around the solar system in the form of comets dirty snowballs of ice dust and rock fragments. It also occurs on other planets but mainly as water vapor or as in this crater near the north pole of Mars as ice. However liquid water may exist beneath the icy surface of Europa one of the moons of Jupiter and where there is water there may be life. 64 LATENT HEAT WATER ON EARTH When water evaporates its molecules absorb energy. This makes them moves faster so they burst apart to form water vapor. This energy is called latent heat. If the vapor condenses into clouds latent .
